<!DOCTYPE html>
<html lang="en">
	<head>
		<title>three.js webgl - multiple canvases - grid</title>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
		<link type="text/css" rel="stylesheet" href="main.css">
		<style>
			html, body {
				height: 100%;
			}

			body {
				background-color: #fff;
				color: #444;
			}

			a {
				color: #08f;
			}

			#centerer {
				display: table;
				width: 100%;
				height: 100%;
			}

			#centerer-cell {
				display: table-cell;
				vertical-align: middle;
			}

			#container {
				margin-left: auto;
				margin-right: auto;
				width: 604px;  /* 300*2 + border; */
			}

			#container div {
				float: left;
			}
			#canvas1, #canvas2, #canvas3, #canvas4 {
				position: relative;
				float: left;
				width: 300px;
				height: 200px;
				outline: 1px solid red;
			}
		</style>
	</head>
	<body>
		<div id="centerer">
			<div id="centerer-cell">
				<div id="container">
					<div class="container-row">
						<canvas id="canvas1"></canvas>
						<canvas id="canvas2"></canvas>
					</div>
					<div class="container-row">
						<canvas id="canvas3"></canvas>
						<canvas id="canvas4"></canvas>
					</div>
				</div>
			</div>
		</div>
		<div id="info"><a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> webgl -  multiple canvases - grid</div>

		<script type="module">

			import * as THREE from '../build/three.module.js';

			const views = [];

			let scene, renderer;

			let mouseX = 0, mouseY = 0;

			const windowHalfX = window.innerWidth / 2;
			const windowHalfY = window.innerHeight / 2;

			init();
			animate();

			//

			function View( canvas, fullWidth, fullHeight, viewX, viewY, viewWidth, viewHeight ) {

				canvas.width = viewWidth * window.devicePixelRatio;
				canvas.height = viewHeight * window.devicePixelRatio;

				const context = canvas.getContext( '2d' );

				const camera = new THREE.PerspectiveCamera( 20, viewWidth / viewHeight, 1, 10000 );
				camera.setViewOffset( fullWidth, fullHeight, viewX, viewY, viewWidth, viewHeight );
				camera.position.z = 1800;

				this.render = function () {

					camera.position.x += ( mouseX - camera.position.x ) * 0.05;
					camera.position.y += ( - mouseY - camera.position.y ) * 0.05;
					camera.lookAt( scene.position );

					renderer.render( scene, camera );

					context.drawImage( renderer.domElement, 0, 0 );

				};

			}

			//

			function init() {

				const canvas1 = document.getElementById( 'canvas1' );
				const canvas2 = document.getElementById( 'canvas2' );
				const canvas3 = document.getElementById( 'canvas3' );
				const canvas4 = document.getElementById( 'canvas4' );

				const w = 300, h = 200;

				const fullWidth = w * 2;
				const fullHeight = h * 2;

				views.push( new View( canvas1, fullWidth, fullHeight, w * 0, h * 0, w, h ) );
				views.push( new View( canvas2, fullWidth, fullHeight, w * 1, h * 0, w, h ) );
				views.push( new View( canvas3, fullWidth, fullHeight, w * 0, h * 1, w, h ) );
				views.push( new View( canvas4, fullWidth, fullHeight, w * 1, h * 1, w, h ) );

				//

				scene = new THREE.Scene();
				scene.background = new THREE.Color( 0xffffff );

				const light = new THREE.DirectionalLight( 0xffffff );
				light.position.set( 0, 0, 1 ).normalize();
				scene.add( light );

				// shadow

				const canvas = document.createElement( 'canvas' );
				canvas.width = 128;
				canvas.height = 128;

				const context = canvas.getContext( '2d' );
				const gradient = context.createRadialGradient( canvas.width / 2, canvas.height / 2, 0, canvas.width / 2, canvas.height / 2, canvas.width / 2 );
				gradient.addColorStop( 0.1, 'rgba(210,210,210,1)' );
				gradient.addColorStop( 1, 'rgba(255,255,255,1)' );

				context.fillStyle = gradient;
				context.fillRect( 0, 0, canvas.width, canvas.height );

				const shadowTexture = new THREE.CanvasTexture( canvas );

				const shadowMaterial = new THREE.MeshBasicMaterial( { map: shadowTexture } );
				const shadowGeo = new THREE.PlaneGeometry( 300, 300, 1, 1 );

				let shadowMesh;

				shadowMesh = new THREE.Mesh( shadowGeo, shadowMaterial );
				shadowMesh.position.y = - 250;
				shadowMesh.rotation.x = - Math.PI / 2;
				scene.add( shadowMesh );

				shadowMesh = new THREE.Mesh( shadowGeo, shadowMaterial );
				shadowMesh.position.x = - 400;
				shadowMesh.position.y = - 250;
				shadowMesh.rotation.x = - Math.PI / 2;
				scene.add( shadowMesh );

				shadowMesh = new THREE.Mesh( shadowGeo, shadowMaterial );
				shadowMesh.position.x = 400;
				shadowMesh.position.y = - 250;
				shadowMesh.rotation.x = - Math.PI / 2;
				scene.add( shadowMesh );

				const radius = 200;

				const geometry1 = new THREE.IcosahedronGeometry( radius, 1 );

				const count = geometry1.attributes.position.count;
				geometry1.setAttribute( 'color', new THREE.BufferAttribute( new Float32Array( count * 3 ), 3 ) );

				const geometry2 = geometry1.clone();
				const geometry3 = geometry1.clone();

				const color = new THREE.Color();
				const positions1 = geometry1.attributes.position;
				const positions2 = geometry2.attributes.position;
				const positions3 = geometry3.attributes.position;
				const colors1 = geometry1.attributes.color;
				const colors2 = geometry2.attributes.color;
				const colors3 = geometry3.attributes.color;

				for ( let i = 0; i < count; i ++ ) {

					color.setHSL( ( positions1.getY( i ) / radius + 1 ) / 2, 1.0, 0.5 );
					colors1.setXYZ( i, color.r, color.g, color.b );

					color.setHSL( 0, ( positions2.getY( i ) / radius + 1 ) / 2, 0.5 );
					colors2.setXYZ( i, color.r, color.g, color.b );

					color.setRGB( 1, 0.8 - ( positions3.getY( i ) / radius + 1 ) / 2, 0 );
					colors3.setXYZ( i, color.r, color.g, color.b );

				}

				const material = new THREE.MeshPhongMaterial( {
					color: 0xffffff,
					flatShading: true,
					vertexColors: true,
					shininess: 0
				} );

				const wireframeMaterial = new THREE.MeshBasicMaterial( { color: 0x000000, wireframe: true, transparent: true } );

				let mesh = new THREE.Mesh( geometry1, material );
				let wireframe = new THREE.Mesh( geometry1, wireframeMaterial );
				mesh.add( wireframe );
				mesh.position.x = - 400;
				mesh.rotation.x = - 1.87;
				scene.add( mesh );

				mesh = new THREE.Mesh( geometry2, material );
				wireframe = new THREE.Mesh( geometry2, wireframeMaterial );
				mesh.add( wireframe );
				mesh.position.x = 400;
				scene.add( mesh );

				mesh = new THREE.Mesh( geometry3, material );
				wireframe = new THREE.Mesh( geometry3, wireframeMaterial );
				mesh.add( wireframe );
				scene.add( mesh );

				renderer = new THREE.WebGLRenderer( { antialias: true } );
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( 300, 200 );

				document.addEventListener( 'mousemove', onDocumentMouseMove );

			}

			function onDocumentMouseMove( event ) {

				mouseX = event.clientX - windowHalfX;
				mouseY = event.clientY - windowHalfY;

			}

			function animate() {

				for ( let i = 0; i < views.length; ++ i ) {

					views[ i ].render();

				}

				requestAnimationFrame( animate );

			}

		</script>

	</body>
</html>
